Ultrasonography in Pelvic Floor Dysfunction

Obstetric anal sphincter injury (OASI) and levator ani muscle (LAM) trauma are common disorders in parous women. Four sonographic signs have been published in cases of OASI: external or internal anal sphincter discontinuity; thickening of external anal sphincter at the area of repair; thinning of internal anal sphincter in the area of rupture in conjunction with thickening opposite the rupture site ("half-moon" sign); and abnormality of mucous folds ("mucosal star sign"). Levator trauma can be asymptomatic, with abnormality arising years later. Discontinuity of the LAM is the main sonographic sign but may appear as increased hiatal area in severe cases.